The present invention relates to a sorter which is provided to an image forming apparatus such as a copier and printer to sort sheets discharged from the apparatus, and more particularly relates to a sorter having a plurality of bins, and the sorter is provided with a stapling device to arrange and staple the sheets in the bin.
For a sheet processing device provided with a stapling device to staple sheets discharged from a copier, printer and the like, a sheet finisher has been utilized which is installed together with an automatic recirculating document handler in order to staple the sheets. However, the aforementioned sheet finisher is disadvantageous because the structure is so complicated and expensive.
(1) In Japanese Patent Publication Open to Public Inspection no. 43457/1989, has been disclosed an apparatus in which a stapling device is provided to a relatively simple bin-moving type of sorter. In the aforementioned apparatus, a stapling device to staple sheets sorted into a bin can be freely moved with regard to the bin.
(2) Another sorter is composed in such a manner that: a fixed type of stapling device is provided to each bin; and the bin is moved to the stapling position so that a bundle of sheets can be stapled.
(3) A sorter disclosed in the official gazette of Japanese Patent Publication Open to Public Inspection No. 244869/1987, is composed in such a manner that: a bin having sheets is moved to a position where a stapling operation can be conducted; the sheets are stapled by a stapling device; and when the sheets in other bins are stapled, the stapling device is moved in a vertical direction.
In the aforementioned sorter of case (1) having a stapling device which can be moved freely, the moving stroke of the stapling device is different according to sheet size. Accordingly, when the vertical spacing of each bin is set large, the sorter size becomes large as a whole, and when the vertical spacing of a bin into which the stapling device is inserted, is extended, the mechanism becomes complicated.
In the aforementioned sorter of case (2), the structure of the sorter is complicated as a whole, and in the case where the vertical spacing of the bin is small, a special stapling device is required.
In the aforementioned sorter of case (3), each bin in which sheets are put, is moved straight along a bin guide at an appropriate time. Accordingly, it is disadvantageous in that the structure becomes complicated.
In any sorters, when the sheets aligned on a bin are moved to a stapling position, or when the stapler is inserted between bins, the bundle of sheets are not fixed at all, so that the sheets are stapled without being aligned before the stapling operation. Accordingly, the bundle of sheets becomes irregular.
The first object of the present invention is to provide a composition by which sheets can be stapled at a constant position even in the case of a relatively simple sorter when the sheets are fixed being aligned just before the bin is moved.
As sorter systems which automatically sort a plurality of sheets (copy sheets) discharged from an image forming apparatus such as a copier, there are a fixed bin system, an all bin shifting system, and a bin opening movement system.
In the case of the fixed bin system, a plurality of copies are made from a plurality of documents by an image forming apparatus in such a manner that: the sheets conveyed from the image forming apparatus are successively received by a receiving section of a sorter; then the sheets are moved to a conveyance section; as shown in FIG. 1, while the sheets are being conveyed, they are successively taken into bins 41 by a sorting guide 36 and a delivery roller 35 which are installed in the receiving portion of the bin 41.
The aforementioned bin fixed system is advantageous in that: a relatively large number of sheets can be put into the bin: the sorter can respond at a high speed; and a plurality of sorters can be connected. Therefore, this type of sorter is frequently applied to a console type of high speed copier. For example, 50 sheets can be stacked in each of the bins for sorting use, and 250 sheets can be stacked on a tray for non-sorting use.
The sheets discharged from the aforementioned image forming apparatus are received by the sorter of the aforementioned bin fixed system, and then conveyed at a high speed in a conveyance passage formed in the sorter into the aforementioned bins through the aforementioned branch means.
When a sheet SA2 of a small size conveyed to the bin at a high speed is discharged, sheet SA2 is branched by the branch means 36, pinched by the paper discharging roller 35 and the conveyance belt 31, and discharged at a high speed as shown in FIG. 25(A). Since the weight of small-sized sheet SA2 (for example, a sheet of B4-size or A4-size) is light, an area of the frictional surface of the sheet is small, so that sheet S2A is carried too far jumping over the uppermost portion of the stacked sheets and does not slip down to a predetermined position. Accordingly, sheet S2A is not contacted with stopper wall 41S of the bin 41, so that the bundle of sheets become irregular. When the following sheets are discharged into the bin 41 under the aforementioned condition, the sheets are bumped with each other and a failure in conveyance such as a jam occurs. The conveyance failure tends to occur when a large number of sheets are stacked in the bin 41. In the case of a sorter provided with a stapler, the irregular bundle of sheets are stapled.
When a large-sized sheet S2B (for example, A3-size or B4-size) is discharged onto the bin 41, sheet S2B comes into contact with the uppermost sheet as shown in FIG. 25(B) since the weight of sheet S2B is heavy and the frictional surface is large, so that the movement of sheet S2B is interrupted. Therefore, the trailing edge of the sheet remains on the upper edge of the stopper wall of the bin 41, so that a jam is caused.
The second object of the present invention is to solve the aforementioned problems, and more particularly to provide a sorter characterized in that: a jam caused by a failure in sheet conveyance can be prevented when sheets are conveyed at a high speed; and the sheets can be positively aligned in the bin.